---
title: 'Component Story Format (CSF)'
isTab: true
tab:
  order: 2
  title: CSF Next (Preview)
---

<If notRenderer="react">

<Callout variant="info">
  CSF Next is currently only supported in [React](?renderer=react) projects.
</Callout>

</If>

<If renderer="react">

<Callout variant="warning" icon="🧪">
  This is a [**preview**](../../releases/features.mdx#preview) feature and (though unlikely) the API may change in future releases. We [welcome feedback](https://github.com/storybookjs/storybook/discussions/30112) and contributions to help improve this feature.
</Callout>

CSF Next is the next evolution of Storybook's Component Story Format (CSF). This new API uses a pattern called factory functions to provide full type safety to your Storybook stories, making it easier to configure addons correctly and unlocking the full potential of Storybook's features.

This reference provides an overview of the API and a migration guide to upgrade from prior CSF versions.

## Overview

The CSF Next API is composed of functions to help you write stories. Note how three of the functions operate as factories, each producing the next function in the chain (`definePreview` → `preview.meta` → `meta.story`), providing full type safety at each step.

### `defineMain`

With CSF Next, your [main Storybook config](../main-config/main-config.mdx) is specified by the `defineMain` function. This function is type-safe and will automatically infer types for your project.

```ts title=".storybook/main.js|ts"
// Replace your-framework with the framework you are using (e.g., react-vite, nextjs, nextjs-vite)
import { defineMain } from '@storybook/your-framework/node';

export default defineMain({
  framework: '@storybook/your-framework',
  stories: ['../src/**/*.mdx', '../src/**/*.stories.@(js|jsx|mjs|ts|tsx)'],
  addons: ['@storybook/addon-a11y'],
});
```

### `definePreview`

Similarly, the `definePreview` function specifies your project's story configuration. This function is also type-safe and will infer types throughout your project.

Importantly, by specifying addons here, their types will be available throughout your project, enabling autocompletion and type checking.

You will import the result of this function, `preview`, in your story files to define the component meta.

```ts title=".storybook/preview.js|ts"
// Replace your-framework with the framework you are using (e.g., react-vite, nextjs, nextjs-vite)
import { definePreview } from '@storybook/your-framework';
import addonA11y from '@storybook/addon-a11y';

export default definePreview({
  // 👇 Add your addons here
  addons: [addonA11y()],
  parameters: {
    // type-safe!
    a11y: {
      options: { xpath: true },
    },
  },
});
```

<Callout variant="info">
  The preview configuration will be automatically updated to reference the [necessary addons](#preview-addons) when installing an addon via `npx storybook add <addon-name>` or running `storybook dev`.
</Callout>

### `preview.meta`

The `meta` function on the `preview` object is used to define the [metadata for your stories](./index.mdx#default-export). It accepts an object containing the `component`, `title`, `parameters`, and other story properties.

```ts title="Button.stories.js|ts"
import preview from '../.storybook/preview';

import { Button } from './Button';

const meta = preview.meta({
  component: Button,
  parameters: {
    // type-safe!
    layout: 'centered',
  }
});
```

<Callout variant="info" icon="💡">

<a name="subpath-imports" />

If you would like to use absolute imports instead of relative imports for your preview config, like below, you can configure that using subpath imports or an alias.

```ts
// ✅ Absolute imports won't break if you move story files around
import preview from '#.storybook/preview';

// ❌ Relative imports can break if you move story files around
import preview from '../../../.storybook/preview';
```

<details>
<summary>Configuration</summary>

Subpath imports are a Node.js standard that allows you to define custom import paths in your project, which you can then use throughout your codebase.

To configure subpath imports, add the following to your `package.json`:

```json title="package.json"
{
  "imports": {
    "#*": ["./*", "./*.ts", "./*.tsx"],
  },
}
```

For more information, refer to the [subpath imports documentation](../../writing-stories/mocking-data-and-modules/mocking-modules.mdx#subpath-imports).

---

Alternatively, you can [configure an alias in your builder](../../writing-stories/mocking-data-and-modules/mocking-modules.mdx#builder-aliases) (Vite or Webpack).

</details>

</Callout>

### `meta.story`

Finally, the `story` function on the `meta` object defines the stories. This function accepts an object containing the [`name`](../../writing-stories/index.mdx#rename-stories), [`args`](../../writing-stories/args.mdx), [`parameters`](../../writing-stories/parameters.mdx), and other story properties.

```ts title="Button.stories.js|ts"
// ...from above
const meta = preview.meta({ /* ... */ });

export const Primary = meta.story({
  args: {
    primary: true,
  },
});
```

#### `<Story>.extend`

You can use the `.extend` method to create a new story based on an existing one, with the option to override or add new properties.

<details>
<summary>Property merging details</summary>

Properties are merged intelligently:

- [`args`](../../writing-stories/args.mdx) are shallow merged
- [`parameters`](../../writing-stories/parameters.mdx) are deep merged, except for arrays, which are replaced
- [`decorators`](../../writing-stories/decorators.mdx) and [`tags`](../../writing-stories/tags.mdx) are concatenated

```ts title="Button.stories.js|ts"
// ...from above
const meta = preview.meta({ /* ... */ });

export const Example = meta.story({
  args: {
    primary: true,
    exampleArray: ['a', 'b'],
    exampleObject: { a: 'a', b: 'b' },
  },
  parameters: {
    exampleArray: ['a', 'b'],
    exampleObject: { a: 'a', b: 'b' },
  },
  tags: ['a'],
});

/* 
 * 👇 Final values applied:
 *    {
 *      args: {
 *        primary: true,
 *        disabled: true,
 *        exampleArray: ['c'],
 *        exampleObject: { a: 'c' }
 *      },
 *      parameters: {
 *        exampleArray: ['c'],
 *        exampleObject: { a: 'c', b: 'b' }
 *      },
 *      tags: ['a', 'b']
 *    }
 */
export const ExtendedExample = Example.extend({
  args: {
    disabled: true,
    exampleArray: ['c'],
    exampleObject: { a: 'c' },
  },
  parameters: {
    disabled: true,
    exampleArray: ['c'],
    exampleObject: { a: 'c' },
  },
  tags: ['b'],
});
```

</details>

```ts title="Button.stories.js|ts"
// ...from above
const meta = preview.meta({ /* ... */ });

export const Primary = meta.story({
  args: {
    primary: true,
  },
});

export const PrimaryDisabled = Primary.extend({
  args: {
    disabled: true,
  },
});
```

#### `<Story>.test`

(⚠️ **Experimental**)

A more ergonomic way to define [tests for your stories](../../writing-tests/index.mdx). While this API is still experimental, it is [documented in the RFC to gather feedback](https://github.com/storybookjs/storybook/discussions/30119) and must be enabled via the [`experimentalTestSyntax` feature flag](../main-config/main-config-features.mdx#experimentaltestsyntax).

```ts title="Button.stories.js|ts"
// ...from above
export const PrimaryDisabled = Primary.extend({ args: { disabled: true } });

// 👇 .test method: Attach tests to a story
//    The test function can run the same code as the play function
PrimaryDisabled.test('should be disabled', async ({ canvas, userEvent, args }) => {
  const button = await canvas.findByRole('button');
  await userEvent.click(button);

  await expect(button).toBeDisabled();
  await expect(args.onClick).not.toHaveBeenCalled();
});
```

## Upgrade to CSF Next

You can upgrade your stories to CSF Next either automatically (from CSF 3) or manually (from CSF 1, 2, or 3). CSF Next is designed to be usable incrementally; you do not have to upgrade all of your story files at once. However, you cannot mix story formats within the same file.

Before proceeding, be sure you're using the latest version of Storybook. You can upgrade your Storybook automatically with this command:

<CodeSnippets path="storybook-upgrade.md" />

### Automatically

You can automatically upgrade all of your project's stories from CSF 3 to CSF Next with this command:

<CodeSnippets path="csf-factories-automigrate.md" />

It will run through each of the manual upgrade steps below on all of your story files.

<details>
<summary>Upgrading from CSF 2 to 3</summary>

You must be using CSF 3 to automatically upgrade to CSF Next. If you are using CSF 2, you can upgrade to CSF 3 first using this command:

<CodeSnippets path="migrate-csf-2-to-3.md" />

</details>

### Manual

You can also upgrade your project's story files to CSF Next manually. Before using CSF Next in a story file, you must upgrade your `.storybook/main.js|ts` and `.storybook/preview.js|ts` files.

**1. Update your main Storybook config file**

Update your `.storybook/main.js|ts` file to use the new [`defineMain`](#definemain) function.

```diff title=".storybook/main.js|ts"
// Replace your-framework with the framework you are using (e.g., react-vite, nextjs, nextjs-vite)
+ import { defineMain } from '@storybook/your-framework/node';
- import { StorybookConfig } from '@storybook/your-framework';

+ export default defineMain({
- export const config: StorybookConfig = {
    // ...config itself is unchanged
+ });
- };
- export default config;
```

**2. Update your preview config file**
<a name="preview-addons" />

Update your `.storybook/preview.js|ts` file to use the new [`definePreview`](#definepreview) function.

<details>
<summary>Which addons should be specified in `preview`?</summary>

The ability for an addon to provide annotation types (`parameters`, `globals`, etc.) is new and not all addons support it yet.

If an addon provides annotations (i.e. it distributes a `./preview` export), it can be imported in two ways:

1. For official Storybook addons, you import the default export:
   `import addonName from '@storybook/addon-name'`

2. For community addons, you should import the entire module and access the addon from there:
   `import * as addonName from 'community-addon-name'`

</details>

```diff title=".storybook/preview.js|ts"
// Replace your-framework with the framework you are using (e.g., react-vite, nextjs, nextjs-vite)
+ import { definePreview } from '@storybook/your-framework';
- import type { Preview } from '@storybook/your-framework';
// 👇 Import the addons you are using
+ import addonA11y from '@storybook/addon-a11y';

+ export default definePreview({
- export const preview: Preview = {
    // ...current config
    // 👇 Add your addons here
+   addons: [addonA11y()],
+ });
- };
- export default preview;
```

**3. Update your story files**

Story files have been updated for improved usability. With the new format:

- Import the preview construct from the Storybook preview file
- The meta object is now created via the [`preview.meta`](#previewmeta) function and does not have to be exported as a default export
- Stories are now created from the meta object, via the [`meta.story`](#metastory) function

<Callout variant="info">
The examples below show the changes needed to upgrade a story file from CSF 3 to CSF Next. You can also upgrade from CSF 1 or 2 using similar steps.
</Callout>

```diff title="Button.stories.js|ts"
+ import preview from '../.storybook/preview';
- import type { Meta, StoryObj } from '@storybook/your-framework';

import { Button } from './Button';

+ const meta = preview.meta({
- const meta = {
    // ...meta object is unchanged
+ });
- } satisfies Meta<typeof Button>;
- export default meta;

- type Story = StoryObj<typeof meta>;

+ export const Primary = meta.story({
- export const Primary: Story = {
    // ...story object is unchanged
+ });
- };
```

Note that importing or manually applying any type to the meta or stories is no longer necessary. Thanks to the factory function pattern, the types are now inferred automatically.

**3.1 Reusing story properties**

<Callout variant="info" icon="💡">

If you are reusing story properties to create a new story based on another, the [`<Story>.extend`](#storyextend) method is the recommended way to do so.

</Callout>

Previously, story properties such as `Story.args` or `Story.parameters` were accessed directly when reusing them in another story. While accessing them like this is still supported, it is deprecated in CSF Next.

All of the story properties are now contained within a new property called `composed` and should be accessed from that property instead. For instance, `Story.composed.args` or `Story.composed.parameters`.

```diff title="Button.stories.js|ts"
// ...rest of file

+ export const Primary = meta.story({
- export const Primary: Story = {
    args: { primary: true },
+ });
- };

+ export const PrimaryDisabled = meta.story({
- export const PrimaryDisabled: Story = {
    args: {
+     ...Primary.composed.args,
-     ...Primary.args,
      disabled: true,
    }
+ });
- };
```

<Callout variant="info">
  The property name "composed" was chosen because the values within are composed from the story, its component meta, and the preview configuration.

  If you want to access the direct input to the story, you can use `Story.input` instead of `Story.composed`.
</Callout>

**4. Update your Vitest setup file**

If you're using [Storybook's Vitest addon](../../writing-tests/integrations/vitest-addon/index.mdx), you can remove your Vitest setup file (`.storybook/vitest.setup.ts`).

If you are using [portable stories in Vitest](../portable-stories/portable-stories-vitest.mdx), you may use a Vitest setup file to configure your stories. This file must be updated to use the new CSF Next format.

<Callout variant="warning">
Note that this only applies if you use CSF Next for all your tested stories. If you use a mix of CSF 1, 2, or 3 and CSF Next, you must maintain two separate setup files.
</Callout>

```diff title="vitest.setup.js|ts"
import { beforeAll } from 'vitest';
// 👇 No longer necessary
- // Replace your-framework with the framework you are using, e.g. react-vite, nextjs, nextjs-vite, etc.
import { setProjectAnnotations } from '@storybook/your-framework';
- import * as addonAnnotations from 'my-addon/preview';
+ import preview from './.storybook/preview';
- import * as previewAnnotations from './.storybook/preview';

// No longer necessary
- const annotations = setProjectAnnotations([previewAnnotations, addonAnnotations]);

// Run Storybook's beforeAll hook
+ beforeAll(preview.composed.beforeAll);
- beforeAll(annotations.beforeAll);
```

**5. Reusing stories in test files**

[Storybook's Vitest addon](../../writing-tests/integrations/vitest-addon/index.mdx) allows you to test your components directly inside Storybook. All the stories are automatically turned into Vitest tests, making integration seamless in your testing suite.

If you cannot use Storybook Test, you can still reuse the stories in your test files using [portable stories](../portable-stories/portable-stories-vitest.mdx). In prior story formats, you had to compose the stories before rendering them in your test files. With CSF Next, you can now reuse the stories directly.

```diff title="Button.test.js|ts"
import { test, expect } from 'vitest';
import { screen } from '@testing-library/react';
- import { composeStories } from '@storybook/your-framework';

// Import all stories from the stories file
import * as stories from './Button.stories';

+ const { Primary } = stories;
- const { Primary } = composeStories(stories);

test('renders primary button with default args', async () => {
  // The run function will mount the component and run all of Storybook's lifecycle hooks
  await Primary.run();
  const buttonElement = screen.getByText('Text coming from args in stories file!');
  expect(buttonElement).not.toBeNull();
});
```

The `Story` object also provides a `Component` property, enabling you to render the component with any method you choose, such as [Testing Library](https://testing-library.com/). You can also access its composed properties ([`args`](../../writing-stories/args.mdx), [`parameters`](../../writing-stories/parameters.mdx), etc.) via the `composed` property.

Here's an example of how you can reuse a story in a test file by rendering its component:

{/* prettier-ignore-start */}
<CodeSnippets path="portable-stories-csf-factory-render.md" />
{/* prettier-ignore-end */}

## Frequently asked questions (FAQ)

### Will I have to migrate all of my stories to this new format?

Storybook will continue to support CSF 1, [CSF 2](../../../release-6-5/docs/api/stories/csf.mdx), and [CSF 3](./index.mdx) for the foreseeable future. None of these prior formats are deprecated.

While using CSF Next, you can still use the older formats, as long as they are not mixed in the same file. If you want to migrate your existing files to the new format, refer to [the upgrade section](#upgrading-from-csf-1-2-or-3), above.

### Will this format work with MDX docs pages?

Yes, the [doc blocks](../../writing-docs/doc-blocks.mdx) used to reference stories in MDX files support the CSF Next format with no changes needed.

### How can I know more about this format and provide feedback?

For more information on this experimental format's original proposal, refer to its [RFC on GitHub](https://github.com/storybookjs/storybook/discussions/30112). We welcome your comments!

</If>